1. Field of the Invention
The present invention relates to phosphors and fluorescent lamps utilizing phosphors, more particularly, phosphors emitting blue light and fluorescent lamps utilizing blue light emitting phosphors.
2. Description of the Related Art
A mixture of three color phosphors emitting red, green and blue lights is utilized as phosphors for a cold cathode fluorescent lamp of three-wavelength-region emitting type whose excitation source is a mercury luminescent line or for a general fluorescent lamp. It is well known that the blue light emitting phosphor is particularly important among the three phosphors because light-emitting characteristics of the blue light emitting phosphor have a great influence on a flux of light and color rendering property. As such blue light emitting phosphor, Eu-activated barium-magnesium-aluminum oxide phosphor (BaMg2Al16O27:Eu) has been widely utilized because of its strong luminous intensity and excellent blue color rendering property.
Although Eu-activated barium-magnesium-aluminum oxide phosphor is widely utilized as a blue light emitting phosphor as described above, it is hard to say that the luminous efficiency of the blue light emitting phosphor is sufficient. When Eu-activated barium-magnesium-aluminum oxide phosphor is utilized as a phosphor of a fluorescent lamp, the luminous intensity of blue light reduces significantly after long lighting hours compared with those of red and green light, resulting in deviation of color which is one of the causes of worsening color rendering property. On the other hand, from the viewpoint of issues concerning energy consumption, disposal of waste materials and environmental pollution, a fluorescent lamp having a longer life with bright color and without deviation of color has been demanded not only from the industries but also from general consumers.
Recently various improvement of characteristics of Eu-activated barium-magnesium-aluminum oxide phosphor has been made, however, sufficient performance has not been obtained yet.
An object of the present invention is to provide a blue light emitting phosphor whose luminous intensity is stronger and luminous intensity reduction after long lighting hours is less as compared with Eu-activated barium-magnesium-aluminum oxide phosphor, when it is utilized as a phosphor of a fluorescent lamp.
Another object of this invention is to provide a fluorescent lamp utilizing a blue light emitting phosphor whose reduction in luminous intensity after long lighting hours is small.
The present invention provides a phosphor represented by the formula (1xe2x88x92x)CaO.xEu(O).yMgO.nSiO2, wherein x, y and n represent number of moles, respectively.
The present invention also provides a fluorescent lamp comprising a phosphor of the present invention.
The present invention further provides a fluorescent lamp of three-wavelength-region emitting type comprising a mixture of a red light emitting phosphor, a green light emitting phosphor and a blue light emitting phosphor, wherein said blue light emitting phosphor is the phosphor of the present invention.